Image Processing Apparatus and Control Method Therefor

1. An image processing apparatus comprising: an acquisition unit that acquires a statistical value of pixel values for each divided region obtained by dividing an input image; a determination unit that compares for each divided region the statistical value of the divided region acquired by the acquisition unit with a first threshold and determines whether the divided region is as color region or a monochrome region; and a re-determination unit that compares a statistical value of an adjacent divided region, which is a divided region, from among divided regions determined by the determination unit as monochrome regions, that is adjacent to the divided region determined by the determination unit as a color region, with a second threshold, by which a divided region is more likely determined as a color region than by the first threshold, for each adjacent divided region, and re-determines whether the adjacent divided region is a color region or a monochrome region.

2. The image processing apparatus according to claim 1 , further comprising a calculation unit that calculates for each adjacent divided region the second threshold on the basis of a statistical value of pixel values of the adjacent divided region and a statistical value of pixel values of a peripheral divided region, which is a divided region on a periphery of the adjacent divided region, from among divided regions determined by the determination unit as monochrome regions.

3. The image processing apparatus according to claim 2 , wherein the calculation unit calculates the second threshold on the basis of a ratio of the number of monochrome pixels to the total number of pixels in a region obtained by combining the adjacent divided region and the peripheral divided region of the adjacent divided region, and the second threshold calculated when the ratio is large is a threshold by which a divided region is more likely determined as a color region than by the second threshold calculated when the ratio is small.

4. The image processing apparatus according to claim 2 , wherein the calculation unit calculates the second threshold on the basis of uniformity of pixel values in a region obtained by combining the adjacent divided region and the peripheral divided region of the adjacent divided region, and the second threshold calculated when the uniformity is high is a threshold by which a divided region is likely determined as a color region than by the second threshold calculated when the uniformity is low.

5. The image processing apparatus according to claim 1 , further comprising a calculation unit that calculates for each adjacent divided region the second threshold on the basis of uniformity of pixel values in an adjacent divided region, wherein the second threshold calculated when the uniformity is high is a threshold by which a divided region is more likely determined as a color region than by the second threshold calculated when the uniformity is low.

6. The image processing apparatus according to claim 2 , wherein the peripheral divided region is a divided region continuous in a horizontal direction or vertical direction with respect to the adjacent divided region.

7. A control method for an image processing apparatus, the method comprising: an acquisition step of acquiring a statistical value of pixel values for each divided region obtained by dividing an input image; a determination step of comparing for each divided region the statistical value of the divided region acquired in the acquisition step with a first threshold and determining whether the divided region is a color region or a monochrome region; and a re-determination step of comparing a statistical value of an adjacent divided region, which is a divided region, from among divided regions determined in the determination step as monochrome regions, that is adjacent to the divided region determined in the determination step as a color region, with a second threshold, by which a divided region is more likely determined as a color region than by the first threshold, for each adjacent divided region, and re-determining whether the adjacent divided region is a color region or a monochrome region.